Guest jjohart Posted February 11, 2004 Share Posted February 11, 2004 HI, I've been having a heat soak condition discussed elsewhere, which I finally managed to drive 11miles to the mechanic to show firsthand. He described it as running "too lean", after he restarted the car 5 mins after shut off and it sputtered, intake popped and needed a long pedal push to make revs even run up and eventually stabilize (30-45secs). He did notice a slightly cracked fuel injector, which must be a bit leaky, but he didn't feel that was the cause of this sputtering. He also checked the fuel pressures, which seemed ok. The thing that I don't understand is that he said there WERE NO adjustments to be made with a fuel injected car to make the car run richer, unless I put on a fuel/air computer. Is he right? There have been a lot of people telling me to make sure the car was running rich/lean, but no one telling me how to adjust. I tend to doubt that's a backyard adjustment, but I'd be willing to try if it were as simple as turning a screw, but I dunno... He's telling me to go to salvage parts for a cylinder temperature sensor, air temperature meter, AFM, etc...I'm getting really p.o'd that the guy won't even solve this "until when it gets warmer, and you'll have this condition more regularly, easier to solve?!" Anyone wanna tell me what I can do with a screwdriver to fix this other than want to put it into the tech's whatever??!!!!? Thanks John Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted February 11, 2004 Share Posted February 11, 2004 An adjustable regulator could help. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted February 11, 2004 Share Posted February 11, 2004 you can adjust the spring tension in the air flow meter. Looser spring, more flap movement for a given amount of air, ECU thinks more air is passing and supplies more fuel. adjustable fuel pressure regulator is another, better option. But really, you need to find out why it's doing that, better to fix the problem than try to bandaid it. Did it just start doing this all of a sudden? Or it's always done it? I say, take it to a place that specializes in nissans (but not a dealership unless you like to pay high prices ) and have them do a diagnostic on the EFI... test all the sensors, the ECU and stuff. Fix that cracked injector of course this will cause problems and make the car not run right. It's probably just a bad sensor, bad airflow meter, or misadjusted airflow meter. Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted February 11, 2004 Share Posted February 11, 2004 Hi, this problem occurred prior to the intercooler install, but is much worse post I/C. I had it checked to make sure there were no leaks (used a smoke test). I've replaced plugs, cap, rotors, wires, tuned, even had injectors cleaned "ultrasonically". I have to think it is something about the I/C the engine's computer doesn't like...can anyone be more specific how to adjust that spring, I don't want to open up the AFM and make things worse! Thanks John Quote Link to comment Share on other sites More sharing options...
Phantom Posted February 11, 2004 Share Posted February 11, 2004 Is your fuel rail cooler blower functioning properly? You're not vapor locking are you? There is a shop in Ft. Worth, TX (too far, I know) that does a "fuel-injection tune-up" on old Z cars. Basically he goes through all the electrical connectors and cleans them up to ensure they are making proper contact. Then he checks the sensors to make sure they are giving the correct outputs and all the emmission control devices to ensure they are operating properly. After that he adjusts the TPS and AFM as required. The point is - somewhere in all that he would find your problem and fix it. That is what you need to do - or have done. Then the engine will run fine. When I had it done on my '77 he charged me $165. It was worth every penny. Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted February 11, 2004 Share Posted February 11, 2004 HI. The injector fan was tested after head work and said to be functional-unless my local half-arsed mechanic didn't bother triple checking. I guess I'm going to have to get an APB for a mechanic slightly closer than TX, but it is tempting! If anyone knows of a mechanic in the NY/NJ/E.PA/CT and N.E region who is honest and knowledgable about old Z cars, pls. let me know, or fwd their name, thanks! John Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted February 12, 2004 Share Posted February 12, 2004 You should be able to hear it running after you shut off the engine... Quote Link to comment Share on other sites More sharing options...
technicalninja Posted February 12, 2004 Share Posted February 12, 2004 Check thread "afm adjustment for more fuel" under fuel delivery. I typed up a modification I have used on non-turbo mild-medium modified motors. This technique will work on turbo cars as well but only for very mild increases in fuel delivery.(fine tuning an AFR). It will not fix your problem. Your car sounds like it was getting sick just before you had an intercooler installed. I don't think the intercooler has anything to do with it but you should be able to remove the tubes attached to engine, reinstall J pipe and eliminate the intercooler for testing purposes. Are you sure that car is lean after warm start? if you had one or more injectors leaking down after car is shut off it could be flooding engine. A way to test- precondition car so it will do its trick, as car is started have someone administer a small amount of carb spray(B12 works best as a fuel) in to a vacuum line (fuel pressure regulator line works good) and see if the car starts and accelerates easier. If it runs easier the your are lean,if it doesn't help or hurts then your rich. Disconnecting fuel pressure regulator vacuum port will make a F.I. run richer during light load operation. Look for fuel in regulator vac line,if found replace regulator. Your description of symptoms sounds most like a bad AFM. Has anyone checked for plate binding at closed position (has to be checked with AFM mounted in car at normal riding position). Getting an extra AFM or borrowing one is not out of the question. Another useful test is the shut down fuel pressure test. When engine is turned off notice fuel pressure(24-28 lbs common). leave car for an hour did fuel pressure drop drastically? A small drop, 2-4 PSI< is expected. A drop to 0 means something in the fuel supply/distribution system is leaking- Common culprit is check valve in fuel pump. Represurise fuel system (crank car untill gauge shows pressure-a good pump will presurise in 1-3 seconds) with car off carefully clamp off fuel inlet line(near filter) with a pair if visegrips. You do not want to clamp too tight-can damage line but you want it tight enough to seal line off. Watch for fuel pressure drop-if still large further testing will be necessary. I have many times removed the injection lines and injectors as a complete set leaving lines attached to find leaking injectors and check injector patterns. Provide power to fuel pump-look for leaks. injectors should not leak at all. Another common issue with air flow controlled F.I. is the integrity of the intake tract. Zs used many flexible rubber tubes with "pleated areas" that get cracks down in the pleats which can be hard to find. The most recent work may have dislodged a hose or made a crack worse. All air which goes in the engine must go through the AFM or incorrect mixtures will result. Common problem occures on F.I. Zs. clutch install causes symptoms like yours. What had happened is engine angle changed when trans was taken off-pulled hose off of AFM. After clutch install complete engine partially reinstalled hose (flush on top-kinked on bottom). Car now has a seriously bad drivabilty problem and from all apperances nothing changed. Customer now thinks mechanic is idiot. Mechanic may be very good- just hasn't seen that particular trick before. Your mechanic is right about no AFR adjustment on stock parts. Nissan and other manufactors do not want normal consumers to alter their settings. I am sure that the cars could never be EPA certified if they were adjustable. Carb mixture adjustment anti-tamper caps have been around for 30 years. Abnormal consumers (me and others like me) can usually find a way to adjust AFR. If a shop modifies an emission control device for profit the crime is a felony punishable by up to 5years Federal and/or $100,000 dollar fine. When asked if I would "gut a cat" I price it at $250,000- have had no takers yet! Most shops which do such thing get away with it but if I'm going to commit what the US goverment thinks is a felony I want to make a lot of money! Typing about modifications is not illegal. If I modify my own car it is a misdemeanor with a minor fine The only factory adjustment is AFM bypass screw which only affects idle AFR. the CTS sensor is cheap-can be tested with info found in Nissan factory manual. I have found many bad ones. also check wiring connection for corrosion. Hope this gives you some testing hints. good luck! Quote Link to comment Share on other sites More sharing options...
Guest jjohart Posted February 12, 2004 Share Posted February 12, 2004 Thanks for all the tips. I do have to ask, b/c now I'm paranoid about not hearing the injector fan come on when the engine is shut off.....is there a minimum engine temp or oil temp that needs to occur for that cooling fan to stay on when I turn off the car? We're in 20-40 degree weather here in MA, and so far as I've been listening the past day, I don't hear that fan coming on at all. My mechanic said that after the head work was done, it had been plugged into the engine temp outlet plug instead of the fan plug, so the fan simply ran all the time (drained my batteries for a day, too!). He said he thought simply reversing the plugs was all that was needed, and indicated maybe it's a faulty sensor. Does the car need to be in Texas to have that aux fan come on? How long should it stay on? What's the easiest way to test it? Thanks John Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted February 12, 2004 Share Posted February 12, 2004 Those injector fans are bad more often than not, in my experience. Many people just remove them and run w/o them w/o any noticeable effect. I haven't run one in 6 years. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted February 12, 2004 Share Posted February 12, 2004 The thing that I don't understand is that he said there WERE NO adjustments to be made with a fuel injected car to make the car run richer, unless I put on a fuel/air computer. Is he right? There have been a lot of people telling me to make sure the car was running rich/lean, but no one telling me how to adjust. Doesnt look like anyone actually answered this question but the answer is yes, he is right. In an EFI vehicle, the computer manages the AFM. The modifications that everyone is talking about above are just that, modifications. Something you should not have to do. I would avoid fixing with modifications and continue searching for the real problem. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted February 12, 2004 Share Posted February 12, 2004 agreed... AFM adjusting and such is more of a fine tuning method to get the most out of an already-good-running car that you've modded for better performance, which many times these old EFI systems dont want to cooperate so you must tweak them, but as I said in my first reply even if you got your car to run better by doing any of these tweaks, it's really just a bandaid covering up a real problem, and that you should rather keep pursuing the problem until you figure out the cause, instead of trying to get around it. Lean/rough running can really only be caused by a few things You either have a vacuum leak or any leak where air can get into the system after the air flow meter... test by spraying around with something like carb cleaner spray while the car runs, spray possible leak areas and if the idle changes you know fluid is getting sucked in thru a leak. Your ignition is not working properly, check your timing with a timing light and revving the engine, see if spark is consistent and smooth. Check that you're getting spark consistently at all six plugs Your EFI is not working properly. There are some ways you can test the EFI system yourself, using a voltmeter, as far as testing sensors and stuff, but the easier way is just to take it to a Nissan place that has the right computer to do it for you. Fuel isn't getting thru the system well enough. Could have a clogged fuel filter or fuel lines, or a clog in the pickup in the tank. Fuel pump may be on the way out. Change the filter, have the lines flushed... worse comes to worse get the tank dropped and cleaned... fuel pump issues will usually make themselves known by the sounds the fuel pump makes when running... usually. Quote Link to comment Share on other sites More sharing options...
Warren Posted February 12, 2004 Share Posted February 12, 2004 According to the FSM EF & EC-78 The auxillary cooling fan (injector fan) is only supposed to come on under the following conditions: Coolant Temperature above 210 degrees and ignition OFF (Normally Aspirated) Coolant Temperature above 216 degrees and ignition OFF (Turbo Equipped) It is NOT supposed to be on when the engine is running. Turning the ignition to the ON position will turn the fan OFF. The fan is only supposed to run for approximately 17 minutes...then it shuts off. To test the circuit's operation, disconnect the harness connector of the water temperature sensing switch. (That's the one with the wire coming out of it under the top radiator hose at the thermostat housing, not the one with the bullet connector on molded in). Connect the lead coming from the harness (on the harness side) to ground...(that simulates that the water temperature has exceeded the preset value)...the fan should come on...until ground is removed or 17 minutes (I really hope it doesn't take 17 minutes to see whether or not the fan motor is running). If the fan comes on, the system is working properly. If the fan doesn't come on, test the fan's operation as below, as well as the fan motor timer unit, located above the fuse box. To test the fan's operation, unplug it and connect 12 volts directly to the leads coming from the fan motor. Hope that clears that part of your question up a little bit. Warren Quote Link to comment Share on other sites More sharing options...
383 240z Posted February 29, 2004 Share Posted February 29, 2004 Did the PM I sent you help at all? Keith Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.